In many commercially important compositions, the consistency of the product is critical to its commercial success. One example is personal care products, which generally contain one or more active ingredients within a carrier formulation. While the active ingredient(s) determine the ultimate performance properties of the product, the carrier formulation is equally critical to the commercial success of the product in that it largely determines the consistency of the product. The rheology of the carrier (also referred to as the "base") largely determines the flow properties of the product, and the flow properties largely determine the manner in which the consumer will apply or use the product.
For example, aluminum chlorohydrate, aluminum-zirconium tetrachlorohydrate, aluminum-zirconium polychlorohydrate complexed with glycine, and aluminum-zirconium complexed with any of trichlorohydrate, octachlorohydrate, and sesquichlorohydrate are metal salts that are commonly used as active ingredients in deodorant and antiperspirant products. Consumers have shown a preference for applying deodorant from a stick form. Thus, the carrier in a stick-form deodorant must be a relatively hard substance, and waxy fatty alcohol such as stearyl alcohol has often been used as the carrier in these products. As another example, the active ingredient in a lipstick is the colorant. A lipstick should not be as hard as a stick deodorant, but of course must maintain its shape when undisturbed at room temperature. A blend of wax and oil is known to provide a consistency that is well-suited as a carrier for a lipstick. As a final example, shampoo desirably has a viscosity greater than water, and when the active ingredient(s) in a shampoo does not have a sufficiently high viscosity, a somewhat viscous carrier material is desirably included in the shampoo formulation.
From the above examples, it is seen that formulators of personal care products depend upon the availability of materials having various rheological properties, in order to formulate a successful personal care product. Materials which have a gel-like character, in that they maintain their shape when undisturbed but flow upon being rubbed, are often desired for personal care products.
Transparent (ie., clear) carriers are desired by formulators who develop a personal care product wherein colorant is an active ingredient, because a transparent carrier (as opposed to an opaque carrier) will minimally, if at all, interfere with the appearance of the colorant. In recent years, consumers have demonstrated an increasing preference for transparent and colorless personal care products such as deodorants and shampoos. There is thus an increasing demand for transparent materials which can provide the Theological properties needed for various personal care products, and particularly which can impart gel-like character to a formulation.
Polyamide resin prepared from polymerized fatty acid and diamine is reported to function as a gellant in formulations developed for personal care products. For example, U.S. Pat. No. 3,148,125 is directed to a clear lipstick carrier composition formed from polyamide resin compounded with a lower aliphatic alcohol and a so-called "polyamide solvent." Likewise, U.S. Pat. No. 5,500,209 is directed to forming a gel or stick deodorant, where the composition contains polyamide gelling agent and a solvent system including monohydric or polyhydric alcohols. Thus, the prior art recognizes to blend certain polyamides with alcohols, to thereby form a gel.
Pure hydrocarbon is desirably included in personal care formulations because it is transparent and relatively inexpensive. Pure hydrocarbons are also available in a wide variety of viscosities and grades. However, pure hydrocarbon often does not have the Theological properties that are desired in a carrier, e.g., it does not naturally exhibit gel-like character. Furthermore, when hydrocarbon is present in a personal care formulation, alcohol is also typically present when a gel-like consistency is desired for the product. Alcohol can be irritating to skin, and accordingly, in some formulations, is desirably omitted.
Accordingly, there is a need in the art for materials which can be combined with pure hydrocarbon to afford a transparent material which has gel-like character. The present invention provides this and related advantages as described herein.